My Carrier high efficiency furnace
All borderline parts can be affected by the difference that outside temp presents because it makes the furnace run more often and for longer.
It probably means though that you might be able to instigate a lockout while testing components by turning up the thermostat high enough to mimic the over night colder conditions.
If you can instigate a lock out on your schedule, then you can at least test out one component per lockout..
Last edited by how; 03-06-2012 at 03:09 PM.